The present invention relates to airplanes and more particularly to a new aerospace plane system, forming the basis for a revolutionary transportation architecture for both point-to-point travel on Earth and access into space with a single vehicle, either manned or unmanned.
The use of liquid hydrogen to condense air has been previously explored. It was first proposed in the 1950s and termed the LACE/separation approach. This approach was further investigated by the Air Force during the early 1960s and by United States Air Force Defense Advanced Research Projects Agency (DARPA/AF) during the National Aerospace Plane (NASP X-30) program in the 1980s-1990s.
There exist many important distinguishing features and advantages of the present invention over the prior art. First, the use of liquid nitrogen (LN2) as a coolant and propellant, as a propellant, LN2 greatly increases propellant density and reduces vehicle volume to achieve a lower drag vehicle, as compared to prior art H2-fueled concepts. Second, combining airbreathing storable oxidizer and a dual-mode rocket engine provides a high Isp (specific impulse) with a high throttleable thrust in a single combustion chamber. Third, liquid pumping instead of an air standard cycle or Brayton cycle minimizes propellant pumping power. Fourth, a minimal airframe/propulsion integration allows for the development of the propulsion system separate from development of the vehicle. Fifth, the present invention can switch between endoatmospheric and exoatmospheric flight at high Isp to allow global reach trajectories which leave the atmosphere or go into orbit. Next, the present invention permits use of rocket propulsion for braking during reentry, reducing weight of the thermal protection system; Lastly, the mass of the present invention slowly decreases during collection allowing flight at a near-constant angle of attack.
The present invention finds application in many commercial, military, and scientific aerospace areas. The concept of the present invention is a dual-mode single stage to orbit propulsion system. Based on the rocket engine but coupled with in-flight air collection, liquefaction, and separation, the proposed system represents a unique combination of existing technologies into a system of vastly improved performance.
During the first airbreathing mode of operation, intake air is initially liquefied in a heat exchanger and condenser using a combination of stored liquid hydrogen (LH2) and stored liquid nitrogen (LN2) as coolants. The liquefied air is then separated into separated liquid oxygen (SLO2) and separated liquid nitrogen (SLN2). It is important to note (and as stated in greater detail below) that while it would be desirous to have perfect separation of the air, it is possible that both SLO2 and SLN2 contain molecules of oxygen and nitrogen as well as other some or all of the other constituents of air. The stored liquid nitrogen is used for cooling and propulsion and is replaced with SLO2, while the SLN2 is pumped back through the heat exchanger and condenser with the stored nitrogen (in what is termed herein as a regeneration process). The SLN2, LN2, and LH2 become gaseous as they passes through the condenser and heat exchanger and are burned in the dual-mode rocket thrust chamber, producing a relatively high thrust and specific impulse. In the second rocket mode, the same thrust chamber is operated as a liquid hydrogen-oxygen rocket, where the liquid oxygen is the SLO2 collected during the first mode.
This system results in a vehicle with a hydrogen-fueled propulsion system that permits takeoff from a runway to any point in less than 2 hours, including circumnavigation or Earth orbit. The development cost of this system is expected to be significantly less than that of the space shuttle. Furthermore, the system has a large potential for continuous improvement in system performance through economical ground-based development and testing of the propulsion subcomponents. The small size and low cost of the propulsion system in accordance with the present invention encourages large fleet size and high flight rate, leading to low operating costs.
Numerous advantages and features of the invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, and from the accompanying drawings.